The present invention relates to sealing structures for divided type cylinder blocks.
Generally, water-cooled engines have a cylinder block including a water jacket defined around the cylinders for circulating coolant. As this cylinder block, a divided type cylinder block having an inner block member and an outer block member has been proposed. The inner block member defines cylinder bores and is assembled with the outer block member by inserting the inner block member into the outer block member from above. With the inner and outer block members assembled with each other, the water jacket is defined between opposing surfaces of the block members. More specifically, in the assembled state of this cylinder block, the outer circumferential surface of a lower end portion of the inner block member is located relatively close to the inner circumferential surface of the outer block member, as opposed to the inner circumferential surface of the outer block member. The clearance defined between the opposed portions of the inner and outer block members is sealed by a liquid gasket. The clearance between. the block members above the sealed clearance defines the water jacket. Accordingly, for preventing coolant from leaking downward from the water jacket, for example, to the interior of the crankcase, the clearance between the opposed portions of the block members, in which the gasket is provided, must have a highly reliable sealing structure.
However, when the inner block member is inserted into the outer block member, the opposed portions of the block members are moved relative to each other along the inserting direction, while located close to each other. In this state, the gasket receives shearing force from the opposed portions and is deformed as smeared along the inserting direction. This prevents the gasket from filling the clearance between the opposed portions sufficiently. If this is the case, the clearance is not sealed reliably.
Japanese Laid-Open Patent Publication No. 2000-145972 describes a sealing structure using a liquid gasket. The sealing structure is employed in a vertically divided type crankcase. More specifically, the sealing structure is used for sealing the clearance defined by an interface (a first interface) between an upper case member and a lower case member and the clearance defined by an interface (a second interface) between the lower and upper case members and a side cover. The first interface extends perpendicular to the second interface. At the crossing section between the first and second interfaces, a recess is provided for retaining the liquid gasket. The gasket in the recess is thus supplied directly to the first and second interfaces, such that the clearance defined by the opposed portions of the upper and lower case members and the side cover is reliably sealed.
However, when inserting the upper case member into the lower case member, the upper and lower case members must be brought close to each other along a direction perpendicular to the interface between the upper and lower case members. Likewise, when the upper and lower case members are joined with the side cover, the case members must be brought close to the side cover along a direction perpendicular to the interface between the case members and the side cover. Therefore, in assembly of the crankcase, the gasket does not receive shearing force from the interfaces. In other words, the sealing structure of the aforementioned publication does not address to the problem of shearing force, which may act on the gasket disposed in the clearances defined by the interfaces when the components are assembled. Accordingly, even if the gasket receives shearing force in assembly of the crankcase, the recess for retaining the gasket cannot contribute to improvement of the sealing performance of the gasket.